Manila is not a particularly demanding airport, though it can get quite busy around the time of night he would have arrived. A320 arrivals often get runway 13 which is 1759m long however I'm pretty sure the landing distance calculations would have required the main 06/24 runway which is 3410m.
There are a considerable number of A320s based in or operating to Manila so maintenance for this type wouldn't be a problem like it would be for a B787.
There is plenty of hotel accommodation available in Manila, and it's under two hours from Hong Kong, making recovery a lot easier.
In the circumstances, Manila would have been my preferred choice as a better and closer option. Failures of one system puts extra strain on those remaining and may bring out problems which were quite happily lying dormant whilst the work was being shared around. A subsequent failure of the Yellow hydraulic system would result in a major downgrade as the remaining Blue system is basically an emergency back up. There are numerous pages of procedures and checklists to wade through in this case.
I would need a very good reason to disregard the advice of the chief pilot and not go to Manila in this situation.